There are a wide variety of self-feeding drilling and machining devices such as self-contained drill units available in the industry for application in varied arrangements and incorporating combinations of electric and compressed air power. For example, U.S. Pat. No. 3,885,635 (which issued to K. Menzel) illustrates a two speed mechanical quill feed and spindle drive mechanism for a machine tool featuring a rotatable spindle mounted on bearings within a quill shaft. A ballscrew arrangement is provided whereby an internally threaded nut is rotated about the helically grooved quill shaft which is restrained against rotation within a housing. A motor mounted parallel to and above the quill provides rotational energy to the nut, thereby causing the quill to be axially displaced. A second motor is mounted in piggy-back style above the quill motor for providing rotational energy via a pulley and belt arrangement to a splined extension portion of a power shaft. The splined extension remains axially fixed while providing rotational energy to the telescoped spindle as it is reciprocated along with the quill.
A similar quill drive arrangement is shown in U.S. Pat. No. 31,627 (which issued to L. Evans). The Evans device is provided with a ballscrew/ball nut arrangement for longitudinal positioning of the quill as a result of rotational energy applied by a quill feed motor mounted above and parallel to the axis of longitudinal movement. A piggy-backed spindle drive motor is mounted above and parallel to the quill feed motor, and supplies rotational energy to a longitudinal drive spline via a similar pulley and belt arrangement. Unlike the Menzel device, however, the Evans quill is longitudinally driven by rotation of the ballscrew relative to an axially fixed ballscrew nut.
Yet another quill drive mechanism similar to the Menzel device is shown in U.S. Pat. No. 3,859,001 (which issued to W. Hoddinott, et al.), which also features a ballscrew quill feed unit wherein longitudinal movement is imparted to the ballscrew and its attached quill by rotation of a longitudinally fixed ballscrew nut. Rotation of the spindle is provided through a spline connection well known in the industry.
While all of these mechanisms provide operable mechanical feed units, and these general principles have been widely incorporated in many automatic production tools, they have all suffered from a variety of common shortcomings. Particularly, self-feeding mechanical quill feed and spindle drive assemblies available heretofore have generally been relatively large and cumbersome as a result of their piggy-back arrangement of drive motors and transmission assemblies. As illustrated in the patents mentioned above, units utilizing electric power for both the quill feed and spindle drive conventionally mounted the separate motors on top of one another and surmounting the housing of the assembly itself.
While at least one ballscrew actuated device available in the industry has featured orienting one of the drive motors in line with the longitudinal axis of the quill and spindle, as with the feed devices set forth in the patents discussed above, the drive motors have been designed to remain longitudinally stationary, and the spindle has been driven via an extensible spline arrangement to accommodate movement of the distal end of the spindle and the quill. Such arrangements added additional weight and moving parts to the system, and ultimately limited the stroke length of the device. The additional housing structure required to fully enclose and protect all of these moving parts also added additional weight and bulk to the assemblies Such housings were often provided in the form of cast iron, making these devices considerably massive and compromising their convenience, adaptability and applicability.
Some of the automatic production tools available in the industry substitute an air powered quill feed system for one or both of the electric motors. While such substitution can serve to reduce the overall size of the actual feed unit itself, it requires a source of compressed gas, feed lines, and air pressure control valves, pistons and the like Moreover, it has been found that air powered quill feed devices have additional power and range limitations in stroke length which can make such units undesirable or inappropriate for many applications.
Another method and apparatus for providing a machine tool which can be selectively displaced relative to a working surface is shown in U.S. Pat. No. 4,358,228 (which issued to G. Stark). Particularly, the Stark machine tool illustrates another device which utilizes a spline-type arrangement for driving a reciprocable spindle, and which utilizes a separate feed spindle which engages a feed nut to vertically displace the entire head part relative to the table for machining operations. The Stark device is exemplary of the relative complexity and size restrictions prohibiting the easy adaptability of many machine tools available in the industry.
Another arrangement wherein the entire head of a multi-spindle drilling machine is reciprocated relative to a work table is shown in U.S. Pat. No. 3,822,958 (which issued to J. Lewis). While Lewis contemplates limited individual adjustment of each drill motor mounted in its reciprocable head, the rack and scroll plate arrangement provided for such adjustment is limited to relatively minor vertical adjustments which are to be preset prior to machining operations.
Consequently, while a relatively wide variety of automatic production tools utilizing various combinations of electric and air powered drive systems have been available in the industry, heretofore, these devices have suffered from slow operation, insufficient stroke length, and/or excessive size or weight restrictions which limited applicability and adaptability. Additionally, most of these devices were difficult to change over to different operations as a result of their size, weight, and complexity.